When deploying the latest version of a script delete unreferenced scripts from the scripts folder

[leidegre]

Right now, every time you deploy a script, a new script folder is created with the new code. This is what let's you, more or less, or load a new script on to the Azure Functions instance. So, it's a feature.

But it's undesirable to leave the old code there forever. The primary reason for this is that we cannot reliably tell if old code is loaded or not. If it is loaded, we cannot reliably delete it.

So, when the first function is run we should check if there are lingering script folders that could be deleted and attempt to delete them. Eventually this will trim out old code but it may take some time because we don't know reliably when a Azure Function instance is restarted.